Vegetation Update Title Page
Yearly Summary
2013
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence (PFO) of submersed aquatic vegetation (SAV) continued to decrease in Lower Pool 4, Pool 8, and Pool 13. In Upper Pool 4 where there was a slight increase in PFO (22.6% to 25.9%). There were also increase seen in Lake Pepin (12.4% to 20.4%) and pool-wide numbers in Pool 4 (43.8% to 46.8%). Lower Pool 4 declined 12.5% from its 2009 high value (83.7%) while Pool 8 declined 18.1% from its high value (88.6%) in 2010. Pool 13 had the smallest overall decline with an 10.3% decrease from a 2009 high value (63.5%). (Table 2, Figure 2).
- Rooted floating leaf (RFV) and emergent (EM) increased in Pools 8 and 13. Both EM and RFV stayed relatively consistent in Upper Pool 4 with declines in Lower Pool 4. (Table 2, Figure 2).
- SAV declined in all strata in Pool 8, except secondary channels and isolated backwater. Pool 13 saw SAV declines in all strata except for contigupous backwaters. After an increase of SAV in main channel borders in Pool 13 in 2012, SAV frequency decreased by 14.2%. Frequency of SAV in all strata in Pool 4 increased or relatively stable with the exception of lower Lake Pepin and lower secondary channels. The largest increase of SAV in Pool 4 was in upper Lake Pepin (16% increase). (Table 3).
- Upper Pool 4 saw a continuing decrease of the frequency of coontail declining 21.2% since 2010. Coontail declined by 8.9 % in Pool 8, while frequencies of Eurasian milfoil and wild celery remained relatively stable. Pool 13 saw decreases in coontail and Eurasian milfoil with a slight increase in wild celery (Table 4).
- Sago pondweed, American lotus and broadleaf arrowhead increased in Pool 8 and 13. Increases in Sago pondweed and arrowhead occurred in Pool 4 as a whole; but, a slight decrease was seen in arrowhead in Upper Pool 4. No American lotus was recorded in upper Pool 4 or Lake Pepin (Table 5).
- In the recent past, high frequencies of aquatic vegetation in upper Pool 4 were associated with TSS levels below 32 mg/L (Figure 3). Low levels of TSS were most likely due to reduced runoff from low precipitation levels.
- More summary statistics including percent frequency, abundance index, and distribution maps along with species information can be interactively generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets you download the summary data for each search. Raw data can be obtained from the Aquatic Vegetation Data Browser.
2012
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- Prior to 2012, analysis of Pool 4 data was divided at mid-Lake Pepin into an Upper and Lower section. Beginning in 2012, Pool 4 will now be divided and presented as three reaches, consistent with the USACE (2000, Habitat Needs Assessment for the Upper Mississippi River) geomorphic reaches.
- The percent frequency of occurrence (PFO) of submersed aquatic vegetation (SAV) continued to decrease in every pool. Upper Pool 4 declined 21.4 % from a recorded high in 2011 (44.0%), while Lake Pepin declined 33.8% from its recorded high value in 2010 (46.2%). Lower Pool 4 declined 11.4% from its 2009 high value (83.7%) while Pool 8 declined 15.6% from its high value (88.6%) in 2010. Pool 13 had the smallest overall decline with an 8.7% decrease from a 2009 high value (63.5%). (Table 2, Figure 2).
- Very little rooted floating leaf (RFV) and emergent (EM) change occurred in upper and lower Pool 4, Pool 8 and Pool 13 since 2011. However from the highest frequencies in 2009, RFV declined 10.4% in Lower Pool 4, 18.3% in Pool 8, and 11.8% in Pool 13. RFV and EM remained absent in Lake Pepin and EM declined 10.4% in upper Pool 4 since 2010. (Table 2, Figure 2).
- SAV declined in all strata in Pool 8, except main channel border, which remained stable. The secondary channels of Pool 8 saw the biggest decline in SAV from 43.1% to 32.3%. Pool 13 saw SAV declines in contiguous and isolated backwaters, and side channels. Main channel borders increased by 5%, and the impounded stratum remained stable. All strata in Pool 4 decreased with the exception of lower pool main and secondary channels, which increased slightly (6 and 7% respectively). The largest decreases of SAV in the Pool 4 were in upper pool backwaters (32% decline) and upper Lake Pepin (21% decline). (Table 3).
- Frequency of coontail remained stable in Pool 8, but declined by over 10% in Pools 4 (12.3%) and 13 (11.9%). Frequencies of Eurasian milfoil and wild celery remained stable in all pools. (Table 4).
- Sago pondweed decreased by over 10% in upper pool 4 (13.2%), Lake Pepin (10.1%), and Pool 8 (15.3%), but remained stable in lower Pool 4 and Pool 13. American lotus and broadleaf arrowhead remained at low but stable PFO in lower Pool 4, Pool 8 and Pool 13. No American lotus was recorded in upper Pool 4 or Lake Pepin.(Table 5).
- In the recent past, high frequencies of aquatic vegetation in upper Pool 4 were associated with TSS levels below 32 mg/L (Figure 3). Low levels of TSS were most likely due to reduced runoff from low precipitation levels.
- More summary statistics including percent frequency, abundance index, and distribution maps along with species information can be interactively generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets you download the summary data for each search. Raw data can be obtained from the Aquatic Vegetation Data Browser.
2011
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence of submersed aquatic vegetation (SAV) decreased in every pool from 2010. Upper Pool 4 (37.6% to 34.5%) and Pool 13 (62.8% to 57.5%) had smaller decreases while lower Pool 4 and Pool 8 both decreased by about 10%. (Table 2, Figure 2).
- Rooted floating leaf (RFV) and emergent (EM) vegetation remained relatively unchanged in upper Pool 4. In lower Pool 4, RFV decreased while EM vegetation increased. RFV and EM decreased in Pool 8. Pool 13 exhibited a decrease in RFV while EM remained stable (Table 2, Figure 2).
- SAV declined in all strata in Pool 13 except Secondary Channel which increase slightly by 2%. Main channel, side channel and Lake Pepin strata all decreased in lower Pool 4 while contiguous backwaters remained stable. Pool 8 saw the the largest decreases in SAV in main channel border (48.6% to 25.7%) and secondary channel (69.2% to 43.1%) (Table 3).
- All-time high frequencies of occurrence of coontail occurred in Upper Pool 4; but declined in all other areas. Frequencies of Eurasian water milfoil and wild celery declined in Pool 8. Wild celery increased from 21.5 to 34.7% in lower Pool 4 but remained relatively stable in Pool 13. (Table 4).
- Sago pondweed increased by over 10% in Pools 8 and 13 but decreased slightly in upper and lower Pool 4 (Table 5).
- In the recent past, high frequencies of aquatic vegetation in upper Pool 4 were associated with TSS levels below 32 mg/L (Figure 3). Low levels of TSS were most likely due to reduced runoff from low precipitation levels.
- Water levels remained elevated above the 1940 to 2010 mean from March to August in all three pools (LTRMP Hydrographs). Most SAV species showed a decline from 2010 with Canadian waterweed showing the largest decline in all three pools.
- Although vegetation monitoring in Pool 4 was completed within the standard time frame, sampling in lower Pool 4 occurred three weeks later than most previous years
due to a Minnesota state government shutdown from July 1 – July 20. Sampling in upper Pool 4 was completed before the shutdown. Because of the sustained high water levels through August, SAV in lower Pool 4 decreased by 10% percent as compared to upper Pool 4, which decreased by only 3%.
- More summary statistics including percent frequency, abundance index, and distribution maps along with species information can be interactively generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets you download the summary data for each search. Raw data can be obtained from the Aquatic Vegetation Data Browser.
2010
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence of submersed aquatic vegetation (SAV) continues to increase to all time highs in each pool. Upper Pool 4 currently has 38%, up from a low of 7% in 2004, while lower Pool 4 has nearly 80% frequency of occurrence. Pool 8 has increased overall from 48% in 2001 to a current high frequency of 88%. Pool 13 increased from a low in 2003 of 40% to its current frequency of 63%, which has remained relatively unchanged from 2005 (Table 2, Figure 2).
- Rooted floating leaf and emergent vegetation remained relatively unchanged in upper and lower Pool 4. In Pool 8 and Pool 13 rooted floating leaf vegetation decreased slightly while emergent vegetation remained stable (Table 2, Figure 2).
- SAV remained relatively stable in all strata in Pool 13. A 30% increase occurred in lower Lake Pepin with little change in Upper Lake Pepin and Pool 4. Lower side channels decreased by 17.5% (72.5 to 55.0%). Pool 8 SAV increased in all strata and by over 10% in BWI, MCB, and SC. All-time high frequencies of occurrence of coontail occurred in Pools 4, 8, and 13. All time high frequencies of Eurasian water milfoil and wild celery occurred in Pool 8, and remained stable in Pools 4 and 13.
- Eurasian watermilfoil decreased by 14% in lower Pool 4 and sago pondweed decreased by 12% in Pool 13. Coontail increased by 15% in Pool 8 and 10% in Pool 13.
- In upper Pool 4, an increase in total suspended solids (TSS) above 32 mg/L was associated with a slight decline in SAV in the MCB and SC of upper Pool 4 (primarily SC). In the recent past, high frequencies of aquatic vegetation were associated with TSS levels below 32 mg/L (Figure 3). Low levels of TSS were most likely due to reduced runoff from low precipitation levels. Water levels in 2006, 2007, and 2009 reflect below average standard elevation.
- Comparing frequencies of Canadian waterweed in Pool 13 to mean turbidity readings observed at LTRMP fixed sites during the peak growing season shows that Canadian waterweed increased as mean turbidity levels dropped below 20 NTU (2005-2007) (Figure 4). In 2008, with elevated turbidity levels across all areas of Pool 13, Canadian waterweed frequencies decreased by 25%. In 2009 and 2010 frequencies rebounded as mean turbidity levels decreased across Pool 13.
- More summary statistics including percent frequency, abundance index, and distribution maps along with species information can be interactively generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets you download the summary data for each search. Raw data can be obtained from the Aquatic Vegetation Data Browser.
2009
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence of submersed aquatic vegetation (SAV) continues to increase to all time highs in each pool. Upper Pool 4 currently has 34%, up from a low of 7% in 2004, while lower Pool 4 has nearly 76% frequency of occurrence. Pool 8 has increased overall from 48% in 2001 to a current high frequency of 80%. Pool 13 increased from a low in 2003 of 40% to its current high frequency of 64%, a slight increase from 2008 (Table 2, Figure 2).
- Rooted floating leaf and emergent vegetation decreased slightly in upper Pool 4 while they both increased slightly in lower Pool 4 and Pool 8. Rooted Floating leaf vegetation increased in Pool 13 while emergent vegetation remained stable (Table 2, Figure 2).
- Emergent vegetation percent frequency of occurrence increased in impounded areas of Pool 8 from 3.8% in 2008 to 14.1% in 2009 (Table 2). In particular, wild rice increased from 0.5% to 4.3%. One contributing factor to the increase in wild rice may have been low discharge in June and July (a critical growth period) for three of the last four years (See LTRMP hydrographs).
- SAV increased by over 30% in isolated backwaters of Pool 13. Increases of over 20% occurred in lower Lake Pepin and 15% in Pool 8 impounded stratum. Increases of approximately 10% occurred in lower Pool 4 main channel borders and secondary side channels (Table 3).
- SAV decreased in Pool 8 contiguous backwaters, main channel borders and had over a 20% decrease in isolated backwaters (Table 3).
- All-time high frequency of occurrence occurred for coontail and Eurasian milfoil in Pools 4 and 8 and wild celery in Pools 8 and 13; although these records are the result of only a slight increase from 2008 (Table 4).
- A closer look at the increase in SAV in upper Pool 4 (specifically main channel borders and secondary channels) along with total suspended solids (TSS) data collected by the LTRMP water quality component suggests when mean summer (Jun-Sept) TSS levels drop below 32 mg/L (i.e. 2006, 2007, and 2009), the SAV responds with increased frequency of occurrence (Figure 3). Low levels of TSS are most likely due to decreased runoff from low precipitation levels. Water levels in Pool 4 during 2006, 2007, and 2009 reflect a below average standard elevation.
- Comparing frequencies of Canadian waterweed in Pool 13 to mean turbidity readings observed at LTRMP fixed sites during the peak growing season shows that Canadian waterweed increased as mean turbidity levels dropped below 20 NTU (2005-2007) (Figure 4). In 2008, with elevated turbidity levels across all areas of Pool 13, Canadian waterweed frequencies decreased by 25%. In 2009 frequencies rebounded as mean turbidity levels decreased across Pool 13.
.
- More summary statistics including percent frequency, abundance index,
and distribution maps along with species information can be interactively
generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets
you download the summary data for each search. Raw data can be obtained
from the Aquatic
Vegetation Data Browser.
2008
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence of submersed aquatic vegetation (SAV) has been steadily increasing in both upper and lower Pool 4 since 2004. Upper Pool 4 SAV is at the highest frequency recorded since sampling began in 1998. Pool 8 SAV increased slightly from 2007 to 2008 while Pool 13 SAV has remained steady since 2006. (Table 2, Figure 2).
- Rooted floating leaf vegetation (RFV) and emergents (EM) have remained steady in upper and lower Pool 4,with emergents reaching an all-time high in contiguous backwaters of upper Pool 4 (Table 2, Figure 2).
- Rooted floating leaf vegetation and emergents declined from 2007 to 2008 in Pools 8 and 13 (Table 2, Figure 2). In Pool 8, the majority of the RFV decline occurred in isolated and contiguous backwaters while most of the decline in Pool 13 was in secondary channels and impounded areas (Table 6). It should be noted that high water levels and elevated turbidity was present in Pool 13 during the sampling season.
- SAV increased by over 20% in Pools 4 and 13 isolated backwaters and Pool 8 main channel borders from 2007 to 2008. Increases of SAV of over 10% were recorded in Pool 8 secondary channels and Pool 13 backwaters from 2007 to 2008. (Table 3).
- Eurasian watermilfoil, an exotic species, declined by over 15% in Pool 13. (Table 4).
- Coontail and wild celery increased by approximately 10% in Lower Pool 4 from 2007 to 2008 (Table 4).
- More summary statistics including percent frequency, abundance index,
and distribution maps along with species information can be interactively
generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets
you download the summary data for each search. Raw data can be obtained
from the Aquatic
Vegetation Data Browser.
2007
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- The percent frequency of occurrence of submersed aquatic vegetation (SAV) has been steadily increasing in both upper and lower Pool 4 since 2004 and Pool 13 since 2003. SAV has remained stable in Pool 8 since 2005 (Table 2, Figure 2).
- Rooted, floating-leaf vegetation (RFV) and emergents (EM) have been on an upward trend in Pool 8 since 2001. In Lower Pool 4, percent frequencies of both EM and RFV have been increasing since 2004. Whereas in Upper Pool 4, only EM vegetation frequencies appear to be increasing, while RFV frequencies remain low. Throughout Pool 13 RFV and EM vegetation have remained constant (Table 2, Figure 2).
- Increases of over 10% occurred in impounded (RFV) and contiguous backwaters (EM) in Pool 4. Secondary channels in Pool 4 showed a large increase (20% in upper pool secondary channels / 9.8% in lower pool secondary channels) in emergent vegetation over the last 2 years. Increases of over 10% occurred in contiguous backwaters and main channel borders areas in upper Pool 4 and Lake Pepin and main channel border areas in lower Pool 4 in 2007 (Table 3).
- SAV and EM vegetation in Pool 13 isolated backwaters decreased by half. Low river levels at the end of July and a planned drawdown of a Wildlife Management Area resulted in dewatered and inaccessible sites (Table 3).
- Wild celery was recorded for the first time in upper Pool 4, in a backwater normally contiguous to Lake Pepin. However, low water during the summer growing seasons has made this location intermittently isolated during the last two years (Table 4).
- In the past 2 years, coontail has increased by more than 10% in Pool 13 (Table 4).
- Nitella spp. (a macroalgae) was recorded for the first time in Pool 8.
- More summary statistics including percent frequency, abundance index,
and distribution maps along with species information can be interactively
generated for all study areas using the Vegetation SRS Graphical Browser. The graphical browser also lets
you download the summary data for each search. Raw data can be obtained
from the Aquatic
Vegetation Data Browser.
2006
- Vegetation sampling was conducted in Pools 4, 8, and 13 (see methods).
- Overall, submersed aquatic vegetation (SAV), rooted, floating-leaf vegetation (RFV), and emergents (EM) remained the same or increased in all study areas (Figure 2).
- The percent frequency of occurrence (hereafter referred to as percent frequency) of SAV, RFV, and EM in Pool 4 increased to the highest level recorded since the study began in 1998 (Table 2).
- The percent frequency of SAV in lower Pool 4 increase 6% from the previous year (57.4% in 2004) and exceeds previously recorded levels of SAV (Table 2). Secondary channels had the largest increase (16.8%; Table 3).
- The percent frequency of SAV in upper Pool 4 remained low (14.6%), although it did increase slightly from the previous 5 years of sampling. The largest increases occurred in the Lake Pepin and main channel border strata (Table 3). Percent frequency of EM increased by 10% in main channel border areas (Table 7).
- Coontail (Ceratophyllum demersum L.) increased in percent frequency by more than 10% in lower Pool 4, Pool 8 and Pool 13 (Table 4).
- The frequencies of coontail, Eurasian watermilfoil (Myriophyllum spicatum L.), and wild celery (Vallisneria americana Michx.) in Pool 4 have all increased to their highest level recorded since 1998 (Table 4).
- Submersed aquatic vegetation, percent frequency and abundance index, has continued to increase in Pool 8 since 2001 (Table 2, Figure 2). Both variables were the highest recorded since the stratified random sampling began in 1998, but were not much different from 2005. However, SAV in secondary channels increased in percent frequency by 13.9% (Table 3). Wild celery has increased steadily since 2001 (Table 4).
- Rooted, floating-leaf and emergent vegetation also remained about the same as 2005 in Pool 8 (Figure 2). A decrease in RFV of 17.5% was recorded in isolated backwaters (Table 6).
- Submersed aquatic vegetation in Pool 13 exhibited the highest percent frequencies in the impounded, main channel border, and secondary channel areas since 1998 (Table 3). Poolwide percent frequency estimates of SAV also reached an all time high (Figure 2).
- The highest percent frequency and percentage of SAV, RFV, and EM were recorded in Pool 13 since the study began in 1998 (Figure 2). Overall, EM percent frequency increased slightly in Pool 13 (Table 2) with the largest increase occurring in isolated backwaters (28%; Table 7).
2005
- Vegetation sampling was only conducted in Pools 4, 8, and 13 (see methods). Pool 26 and La Grange Pool were removed from yearly monitoring because of the lack of submersed aquatic vegetation.
- Sample size was adjusted based on the variance from the previous year
(Table 1) but was capped at 450 sites per pool.
- Overall, submersed aquatic vegetation (SAV) and rooted, floating-leaf
vegetation (RFV) increased in all study areas.
- The percent frequency of occurrence (hereafter referred to as percent frequency) of SAV in Pool 4 increased to
levels not seen since 2001 (Table
2). Percent cover of RFV was near the highest ever recorded (Table
2; Figure 2), although emergent
vegetation declined (Table
2; Figure 2).
- The percent frequency of SAV in lower Pool 4 experienced a 10% increase
(to 57.4%) from the previous year (46.4% in 2004), and exceeds previously
recorded levels of SAV (Table
2).
- The percent frequency of SAV in upper Pool 4 remained low (10%), although
it did increase slightly from the previous 4 years of sampling. This
pattern is most pronounced in the backwater contiguous and upper Lake
Pepin strata (Table 3).
- The frequencies of coontail (Ceratophyllum demersum L.), Eurasian watermilfoil (Myriophyllum spicatum L.), and wild celery
(Vallisneria americana Michx.) in Pool 4 have all increased to their highest level recorded since 1998
(Table 4), whereas
the frequency of sago pondweed (Stuckenia pectinatus [L.] Boerner) has reached its lowest level since 1998
(Table 5).
- Submersed aquatic vegetation percent frequency and abundance index
has continued to increase in Pool 8 since 2001 (Table
2, Figure 2). Both variables
were the highest recorded since the stratified random sampling began
in 1998. Most of the increase occurred in the impounded stratum (Table
3).
- Rooted, floating-leaf and emergent vegetation also increased in Pool
8, but to a lesser degree (Figure
2). Canadian waterweed (Elodea canadensis Michx), narrow-leaf pondweeds (Potamogeton spp. L.), water stargrass (Heteranthera dubia [Jaqc.] MacM.), and
coontail percent frequencies all increased by more than 10% from 2004
to 2005.
- Submersed aquatic vegetation in Pool 13 exhibited the highest percent
frequencies in the contiguous and isolated backwater and impounded areas
since 1998 (Table 3). Poolwide
percent frequency estimates of SAV reached an all time high also (Figure
2).
- Rooted, floating-leaf species covered the highest percentage of shallow
water areas (water less than 3 m) in the contiguous and isolated backwaters
since 2001 (Table 6). One possible cause is that Pool 13 and most of the area south experienced a natural
drawdown this year due to the lack of rain allowing rooted, floating-leaf species to become established.
- More summary statistics including percent frequency, abundance index,
and distribution maps along with species information can be interactively
generated for all study areas using the
Vegetation SRS Graphical Browser. The graphical browser also lets
you download the summary data for each search. Raw data can be obtained
from the Aquatic
Vegetation Data Browser.
2004
- In 2004, aquatic vegetation sampling was conducted in LTRMP key Pools
4, 8, 13, and 26 of the Mississippi River and La Grange Pool of the
Illinois River. Sample size was adjusted based on the variance from
the previous year (Table 1).
Submersed Aquatic Vegetation
- Since 1998, poolwide percent frequency of occurrence of SAV in Pools 8, 13, and 26 has remained relatively
stable (Figure 2).
- Pool 13 recorded the highest percent frequency of SAV since stratified
random sampling began in 1998 (Table
2).
- In upper Pool 4, the percent frequency of SAV declined steadily from
1998 (22%) to 2001 (7%) and has remained low. This pattern is most pronounced
in the backwater contiguous and upper Lake Pepin strata (Table
3).
- Wild celery in Pools 8 and 13
has steadily increased in percent frequency from 1998 (10% and 15%;
respectively) to 2004 (25% and 19%; respectively). Contrastingly in
lower Pool 4, wild celery has declined to a new low (20.1%) since 1998
(Table 4).
- In the backwater isolated strata of the lower Alton Pool of the Illinois
River, SAV increased in percent frequency from 2002 (6%) to 2003 (25%)
then declined to 2% in 2004. All other strata had little or no SAV (Table
3). This same pattern was noted for sago pondweed (Table
5) in the lower Alton Pool of the Illinois River as well as rooted, floating-leaf (Table 6) and emergent species
(Table 7).
- Percent frequency of SAV in the impounded strata of Pool 8 has increased
from 2001 (37%) to 2004 (56%). This may be due in part to the building
of islands in lower Pool 8 providing protection from wind and wave action.
Rooted, Floating-leaf Vegetation
- In Pools 4, 8, and 26 and La Grange Pool, RFV has remained relatively stable from 1998 to 2004 (Figure
2).
- In Pool 13, an increase in RFV has been occurring from 1998 (18%)
to 2004 (27%;Figure 2).
Emergent Vegetation
- In Pools 4, 8, and 13, and La Grange Pool, emergent vegetation has remained
relatively stable from 1998 to 2004 (Figure
2).
- In lower Pool 26, emergent vegetation has shown a slight increase trend
from 2001 to 2004 (Figure 2).
- A water level drawdown was conducted in Pool 8 in 2001 and 2002. In
2001, Pool 8 remained above flood stage until late June, and water was
not drawn down until early July. Percent frequency of emergent vegetation
showed little change from 2000 (12%) to 2001 (10%) then increased in
2002 (16%) and remained steady in 2003 (18%) and 2004 (17%). The increase
in emergent vegetation in 2002 may have resulted from the drawdowns
conducted in 2001 and 2002.
2003
- In 2003, 650 sites were sampled in Pool 8 and 580 in Pool 13. Because
of budget reductions, no aquatic vegetation sampling was conducted in
Pools 4 and 26 and La Grange Pool. However, aquatic vegetation was sampled
from the three pools by other agencies using LTRMP protocols, and the
data were graciously provided to the LTRMP. Pool 26 was
sampled by the Illinois Natural History Survey under a grant provided
by the National Great Rivers Research and Education Center. La Grange
Pool was sampled by the Illinois Natural History Survey under a grant
provided by the Illinois Department of Natural Resources. Aquatic vegetation
data from Pool 4 was provided by the U.S. Fish and Wildlife Service
and the Division of Fisheries, Minnesota Department of Natural Resources.
- Submersed aquatic vegetation (SAV) was most frequently collected
in lower Pool 4 (58% of the sites) and in Pools 8 (55%) and 13 (41%; Table
2). Lower Alton Pool (21%) and upper Pool 4 (9%) had a moderate
amount,whereas no SAV was found in Pool 26 and La Grange Pool.
Abundant SAV was recorded in the lake stratum of La Grange Pool (93%;
Table 3). The lake
stratum was not included in the poolwide estimate for La Grange Pool
because the lakes were located behind large agricultural levees and
were never flooded by the Illinois River.
- The SAV frequency has remained fairly constant from 1998 to 2003
in lower Pool 4, in Pools 8, 13, and 26, and La Grange Pool (Figure
2). Upper Pool 4 SAV has shown a steady decline since 1998,
whereas the SAV in lower Alton Pool increased by 16% from 2002 to 2003.
- Coontail was frequently observed
in lower Pool 4 (32%) and in Pools 8 (31%) and 13 (27%) in 2003 (Table
4). Coontail was rarely observed in upper Pool 4 (3%) and
in lower Alton Pool (3%) and not recorded in Pool 26 and La Grange Pool.
Eurasian watermilfoil and wild celery
were abundant in Pool 4, common
in Pools 8 and 13, and rare or absent in upper Pool 4, Pool 26, and La
Grange Pool (Table 4).
Sago pondweed was most
frequently observed in Pool 13 (19%) followed by lower Alton Pool (16%),
Pool 8 (14%), lower Pool 4 (11%), and upper Pool 4 (7%). No sago
pondweed was recorded in La Grange Pool (Table
5).
- American lotus (Nelumbo lutea Willd.) was most frequently recorded in Pool 13 (23%), whereas
broadleaf arrowhead (Sagittaria latifolia Willd.) was most frequently recorded in Pool 8 (10%; Table
5). Both were recorded in less than 10% of the sites in all
other pools.
- Rooted, floating-leaf vegetation was common in lower Pool 4
(28%), in Pools 8 (21%) and 13 (27%), infrequent in lower Alton Pool
(13%), and rare in upper Pool 4 (3%), Pool 26 (2%), and La Grange Pool
(1%; Table 2).
- The RFV has remained constant in upper Pool 4, in Pools 8 and 26, and in La
Grange Pool and lower Alton Pool (Figure
2). Lower Pool 4 RFV increased 11% from 2001 to 2003. Pool 13 showed a small but steady increase in RFV from 1998 to 2003.
- Emergents were most common in lower Alton Pool representing an increase
of 17% from 2002 to 2003 (Table
2). Emergents were infrequently observed within the sampling
area in lower Pool 4 (14%), in Pools 8 (18%), 13 (7%), and 26 (7%), and
rarely observed in La Grange Pool (3%). No emergents were recorded
in upper Pool 4 in 2003.
- With the exception of lower Alton Pool, frequency of emergent vegetation
has remained fairly constant in all pools from 1998 to 2003 (Figure
2).
- Within all pools, all three life forms were more common in areas of
low flow (contiguous and isolated backwaters) than higher flow (impounded,
secondary channels, and main channel border; Tables 3,
6, and 7;
respectively).
Content manager: Danelle Larson
Page Last Modified:
October 10, 2019
